1. Field of the Invention
The present invention relates to image-data scaling systems which can be suitably used in an image scanner, a digital copying machine, a facsimile machine, an image editing system and so on and, more particularly, to an image-data scaling system in which a digital image data is magnified or reduced to a desired size through digital logic processing with respect to a main scanning direction.
2. Description of the Related Art
As a prior art original-image scaling system, there is an optically scaling system. The prior art optical system however has had such defects that it is difficult to attain a wide range of scaling control and further accurate mechanisms are required for mechanical and optical adjustments, which causes the system to be made large in size and expensive in cost.
To avoid this, there have been recently suggested various sorts of scaling systems in which a unity original data is subjected to an electrical scaling operation to thereby obtain a data having a desired magnification. It is importantly demanded in these electrical scaling systems that the desired-scaled image data must be synchronized with the data clock of the original input image data at any magnification so that the desired-scaled image data can be obtained on a real time basis to thereby enable to process the scaled image data by a raster scanning type apparatus.
For the purpose of satisfying such a demand, there have been proposed such scaling systems as disclosed in Japanese Patent Appln. Laid-Open Nos. 62-256179, 62-257274 and 62-257275. These scaling systems are arranged mainly on a software basis, and more specifically, are arranged so that the position of a sampling point after scaling is first determined, a data of an original image in the vicinity of the new sampling point is picked up, a distance between the new sampling point and the picked-up original image data position is determined, and then a desired-scale image data is calculated on the basis of the distance and the picked-up original image data. With the above prior art systems, two RAMs are used so that while a data is written into one RAM, a data is read out from other other RAM, which is switched for every line.
Other exemplary prior art scaling systems are arranged so that the systems are mainly arranged on a hardware basis, i.e., so as basically to control the reading operation of a line memory in an enlargement mode and to control the writing operation of the line memory in a reduction mode, as disclosed in Japanese Patent Appln. Laid-Open Nos. 63-48064 and 63-82168. Even in these systems, two RAMs are used so that while a data is written into one RAM, a data is read out from the other RAM, which is alternately repeated.
In this way, the prior art optical scaling systems have had such defects that any of the systems becomes large in size, high in cost and narrow in scaling range, and also that the system circuit becomes large in scale and expensive because of different processing methods for scaling factors above 100% and below 100%.